suibianwanwank commented on code in PR #4614:
URL: https://github.com/apache/calcite/pull/4614#discussion_r2498643868
##########
core/src/main/java/org/apache/calcite/sql2rel/RelDecorrelator.java:
##########
@@ -804,17 +804,18 @@ protected RexNode removeCorrelationExpr(
}
}
+ final Correlate correlate = frameStack.peek() == null ? null :
frameStack.peek().left;
if (rel.getGroupType() == Aggregate.Group.SIMPLE
&& rel.getGroupSet().isEmpty()
&& !frame.corDefOutputs.isEmpty()
&& (
// If there is a COUNT, we must call rewriteScalarAggregate (to
distinguish 0 vs empty)
hasCount
||
- // Otherwise call only for non-LEFT Correlate, because for LEFT:
NULL is effectively
- // the same as empty (which promotes NULL on the RHS)
+ // Otherwise call except if this is a LEFT Correlate with the
Aggregate being its RHS,
+ // in that case NULL is effectively the same as empty (which
promotes NULL on the RHS)
(!parentPropagatesNullValues
- && requireNonNull(frameStack.peek()).left.getJoinType() !=
JoinRelType.LEFT))) {
Review Comment:
LGTM, An additional thought is whether an inner join would also work.
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